PICS: BIBI FUNYAL The walled city of Lo-Manthang with the Annapurnas dominating the horizon far to the south.

Nepal may be a republic, but Mustang is still a kingdom. Here in the arid trans-Himalayan district on the Tibetan plateau, water is a precious commodity. Every year, the hardy and devout inhabitants of this cold and high desert undertake a divine ritual to ensure water for the coming year. The Mustang water festival commemorates the deity Dorje Jono's defeat of his demon father Tenchi, who refreshes the pools of Mustang and restores the glory of its people.

The ancient legend of Tenchi gives life to a three-day festival here in Lo Manthang every May. Like many religious events, the celebration coincides with the changing seasons and the Mustangis re-enact the myth through dancing, gun fire and horn blowing to banish the demons and usher the rains.

French ethnologist Michel Peissel was the first westerner to observe the Tenchi festival in 1964. "The scenes I witnessed were so extraordinary and so unexpected that I dared not believe my eyes and even today I have some trouble in believing in the reality of what I saw that day," Peissel wrote.

The traditional circle dance is performed in front of Raja Jigme Prabal Bista's palace.

An elder onlooker with his prayer wheel.

A monk chants mantras to evoke the god of rain

Monks herald in the festivities with traditional horns.